In general, an instantaneous coupling device comprises a tubular body and means for retaining a pipe end in leaktight manner in the body. Said means comprise a retaining member arranged to receive the pipe end, and cam means interposed between the body and the retaining member to bring the retaining member from a release state in which it releases the pipe end to a grip state in which it grips the pipe end, on the retaining member being moved axially inside the body between a first position and a second position.
A retaining member in common use is constituted by a tube having longitudinal slots formed in one end thereof individualizing claws that are deformable in bending between the release state in which they define an inside diameter greater than or equal to an outside diameter of the pipe end, and a grip state in which they define an inside diameter smaller than the outside diameter of the pipe end.
The cam means are generally constituted by an inside surface of frustoconical shape formed in the wall forming the tubular body and centered on the axis of the tubular body.
Coupling devices constructed in that way are very effective. Nevertheless, the amplitude of deformation of the claws, and thus the difference between the minimum and maximum inside diameters defined thereby, is limited by the thickness of the wall of the tubular body in which the frustoconical surface is defined. The outside diameter of pipes usable with any given coupling device an therefore vary only very little, otherwise it is no longer guaranteed that the retaining member will grip the pipe end firmly.
Furthermore, claw retaining members, also known as clamps, must be made of a material that is sufficiently flexible to enable the claws to deform, while also being sufficiently hard to enable the claws to penetrate into the pipe end. When the pipe end is made of a relatively hard plastics material, the material used for making the clamp is a thermosetting material. Nevertheless, such a material is not recyclable and allows only slow rates of manufacturing throughput. When the material constituting the pipe end is relatively flexible, the clamp is made of flexible thermoplastic material. The use of a flexible thermoplastic material is more advantageous in terms of manufacture and recyclability of the clamp, but is nevertheless limited in terms of the claws having relatively small ability to penetrate into the pipe end. Hard thermoplastic materials are not suitable for use in making such clamps because of the risk of the claws breaking when being deformed between their two states.